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Proposal Information for 2014B-0076


PI: Thomas Maccarone, Texas Tech University, thomas.maccarone@ttu.edu
Address: Department of Physics, Texas Tech University, Lubbock TX, 79409, United States

CoI: James Steiner, Harvard-Smithsonian Center for Astrophysics
CoI: Jeffrey McClintock, Harvard-Smithsonian Center for Astrophysics
CoI: Jerome Orosz, San Diego State University
CoI: Dominic Walton, Caltech Astronomy

Title: Determining the mass of a putative heavy stellar black hole

Abstract: IC 10 X-1, a bright eclipsing X-ray binary with a Wolf-Rayet star donor in the star forming galaxy IC 10, has shown a large radial velocity amplitude, implying that its black hole is about 30 solar masses, about twice as large as any stellar mass black hole in the Milky Way. In the Milky Way Wolf-Rayet X-ray binary Cygnus X-3, radial velocity curves made from the donor star's emission lines are out of phase with the photometric variability for the system. A model for that system indicates that its wind is photoionized by the X-ray source, so only the part of the wind shielded by the donor star itself produces line emission, meaning that the radial velocity amplitude is a convolution of the wind speed and the orbital speed. If the same is true for IC 10 X-1, then its black hole mass has been overestimated. Taking three Gemini spectra close in time to a scheduled Chandra observation will allow phasing up the radial velocities relative to the X-ray eclipses, and testing whether past radial velocity curves are robust.


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